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| United States Patent |
5,686,366
|
|
Koyama
, et al.
|
November 11, 1997
|
Process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic
composite
Abstract
A platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite consists of
Al.sub.2 O.sub.3 powder, promoters and controllers. The composite is
prepared by mixing aluminum oxide powder with promoters and controllers.
The mixture is shaped and sintered to form an object. In one embodiment of
the invention, the promoters are either salts or oxides of alkaline metals
and alkaline earth metals. The salts are oxidized during sintering.
| Inventors:
|
Koyama; Takashi (Omiya, JP);
Niihara; Koichi (Hirakata, JP)
|
| Assignee:
|
Mitsubishi Materials Corporation (Tokyo, JP)
|
| Appl. No.:
|
285193 |
| Filed:
|
August 3, 1994 |
Foreign Application Priority Data
| Apr 23, 1992[JP] | 4-129973 |
| Apr 27, 1992[JP] | 4-134273 |
| Apr 27, 1992[JP] | 4-134274 |
| Apr 27, 1992[JP] | 4-134275 |
| Apr 27, 1992[JP] | 4-134276 |
| Current U.S. Class: |
501/127; 501/105 |
| Intern'l Class: |
C04B 035/111 |
| Field of Search: |
501/89,105,127,153
51/309
264/65
|
References Cited
U.S. Patent Documents
| 4331048 | May., 1982 | Dworak et al. | 501/105.
|
| 4829028 | May., 1989 | Seki et al. | 501/105.
|
| 5277702 | Jan., 1994 | Thibault et al. | 501/153.
|
Primary Examiner: Group; Karl
Attorney, Agent or Firm: Kohli; Vineet, Morrison; Thomas R.
Parent Case Text
This is a divisional of application Ser. No. 08/049,204 filed on Apr. 19,
1993, now U.S. Pat. No. 5,403,795.
Claims
What is claimed is:
1. A process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic
composite, which comprises:
blending Al.sub.2 O.sub.3 powder with from 0.02 to 4 weight percent of a
first additive for promoting platelet formation in .alpha.-Al.sub.2
O.sub.3 grains, wherein said first additive is at least one oxide of a
member selected from the group, consisting of Li, K, Na, Ca, Sr, Si, and
Ba;
adding from 5 to 40 weight percent of a second additive for controlling
grain growth of said .alpha.-Al.sub.2 O.sub.3 platelets, wherein said
second additive is at least one member selected from the group consisting
of ZrO.sub.2 HfO.sub.2, SiC whiskers, SiC particles and carbides, nitrides
or carbonitrides of IVa, Va or VIa metals;
said Al.sub.2 O.sub.3, said first additive and said second additive forming
a mixture; and
sintering said mixture to produce said platelet .alpha.-Al.sub.2 O.sub.3
based ceramic composite.
2. A process as in claim 1, wherein said sintering is carried out at a
temperature ranging from about 1300.degree. C. to about 1900.degree. C.
3. The process according to claim 1, wherein:
said first additive ranges from about 0.02 to about 2 weight percent of
said .alpha.-Al.sub.2 O.sub.3 mixture.
4. The process according to claim 1, wherein said second additive is at
least one member selected from the group consisting of partially
stabilized ZrO.sub.2, and partially stabilized HfO.sub.2 ; and
said partially stabilized HfO.sub.2 and ZrO.sub.2 further include a solid
solution containing at least one member selected from the group consisting
of Y.sub.2 O.sub.3, MgO, CaO, and CeO.sub.2.
5. A process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic
composite, comprising:
blending Al.sub.2 O.sub.3 powder with from 0.02 to 4 weight percent of a
first additive for promoting platelet formation in .alpha.-Al.sub.2
O.sub.3 grains and from 5 to 40 weight percent of a second additive for
controlling grain growth of said .alpha.-Al.sub.2 O.sub.3 selected from
the group consisting of ZrO.sub.2, HfO.sub.2, SiC whickers, SiC particles
and carbides, nitrides or carbonitrides of IVa, Va and VIa metals, to form
a raw powder composition;
said first additive is selected from the group consisting of salts of
alkali metals, salts of alkaline earth metals which upon heating decompose
into oxides, SiO.sub.2 and a compound which produces SiO.sub.2 ;
heat treating a portion said raw powder composition at a temperature
1000.degree. C. to about 1500.degree. C., to produce a liquid phase
component;
grinding said liquid phase component to produce a liquid phase powder;
mixing the remainder of said raw powder composition and said liquid phase
powder forming a powder shape; and
sintering said powder shape to produce platelet .alpha.-Al.sub.2 O.sub.3
based ceramic composite.
6. The process according to claim 5, wherein the step of heat treating is
carried out at a temperature ranging from about 1000.degree. C. to about
1,050.degree. C.
7. The process according to claim 5, wherein said sintering is carried out
at a temperature ranging from about 1300.degree. C. to about 1900.degree.
C.
8. The process according to claim 5, wherein said salts of alkali metals
are chlorides, carbonates, nitrates, sulfates or oxylates of at least one
selected from the group consisting of Li, K and Na.
9. The process according to claim 5, wherein said salts of alkaline earth
metals are chlorides, carbonates, nitrates, sulfates or oxylates of at
least one selected from the group consisting of Ca, Sr and Ba.
10. The process according to claim 5, wherein said first additive is Si
alkoxide, which upon heating decomposes to produce SiO.sub.2.
11. The process according to claim 5, wherein said Al.sub.2 O.sub.3 powder
has an average particles size of about 0.3 .mu.m.
12. The process according to claim 5, wherein said first additive has an
average particles size of from 0.1 to 5 .mu.m.
13. A platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite according
to claim 1, wherein said .alpha.-Al.sub.2 O.sub.3 based ceramic composite
comprises grains having a longer diameter of up to 15 .mu.m.
14. A platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite according
to claim 5, wherein said .alpha.-Al.sub.2 O.sub.3 based ceramic composite
comprises grains having a longer diameter of up to 15 .mu.m.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an .alpha.-aluminium oxide (hereinafter
referred to as ".alpha.-Al.sub.2 O.sub.3 ") based ceramic composite which
exhibits superior wear-resistance and improved toughness and is almost
free from breakage or chipping of a cutting edge not only when
continuously cutting steel or cast iron, but also when discontinuously
cutting steel or cast iron, which requires a high toughness, together with
excellent cutting performance.
2. Description of the Related Art
The conventionally known ceramic materials for this purpose include
Al.sub.2 O.sub.3 --ZrO.sub.2 ceramics and Al.sub.2 O.sub.3 --ZrO.sub.2
--MgO, Y.sub.2 O.sub.3 and CeO.sub.2 ceramics disclosed in Japanese Patent
Publication No. 59-6,274, which have microstructures an example of which
is shown in the structural photograph based on a scanning-type electron
microscope given in FIG. 1. These ceramics are used for cutting tools
mainly for continuous cutting of steel.
Conventional Al.sub.2 O.sub.3 --ZrO.sub.2 ceramics cannot fully satisfy
these requirements because of the easy occurrence of chip in discontinuous
cutting of steel, for example.
As disclosed in Japanese Patent Provisional Publication No. 61-53,154, on
the other hand, there are also known Al.sub.2 O.sub.3 --ZrO.sub.2 --MgO,
Y.sub.2 O.sub.3, CeO.sub.2 --TiC, TiN, TiCN and SiC ceramics, which tend
however to easily cause easily chips when used for discontinuous cutting
of steel.
In addition, Japanese Patent Provisional Publication No. 2-283,661
discloses .alpha.-Al.sub.2 O.sub.3 --CeO.sub.2 ceramics used as grinding
grains for polishing.
Furthermore, Japanese Patent Provisional Publication No. 4-238,861
discloses ZrO.sub.2 -.alpha.-N.sub.2 O.sub.3 .beta.Al.sub.2 O.sub.3
ceramics. However .beta.-Al.sub.2 O.sub.3 which takes the form of acicular
grains, cannot be used as a matrix component material because of the
content of from 3 to 10 vol. %.
A paper appearing in J. Am. Ceram. Sec., 73›7! 2077-85 (1990) reports that
addition of combinations of Na.sub.2 O and SiO.sub.2, CaO and SiO.sub.2
SrO and SiO.sub.2 or BaO and SiO.sub.2 to Al.sub.2 O.sub.3 powder and
sintering of the mixture causes abnormal grain growth of .alpha.-Al.sub.2
O.sub.3 grains. The grains having abnormally grown have a plate-like shape
with a particle size of over 100 .mu.m and an aspect ratio of at least 5,
according to the report.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention relates to an .alpha.-Al.sub.2 O.sub.3 based ceramic
composite having excellent toughness and being almost free from breakage
or chipping of the cutting edge not only when continuously cutting steel
or cast iron, but also when discontinuously cutting steel or cast iron,
which requires a high toughness, displaying an excellent cutting
performance.
In the present invention, strength and toughness of ceramics are improved
by adding components controlling grain growth of .alpha.-Al.sub.2 O.sub.3
platelets (hereinafter referred to as "Controllers") and additives
promoting .alpha.-Al.sub.2 O.sub.3 platelet formation (hereinafter
referred to as "promoters") in trace amounts to .alpha.-Al.sub.2 O.sub.3
matrix itself converted into platelet-shaped grains, and wear resistance
is increased by coating the surface thereof with a hard layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a microstructural photograph of conventional Al.sub.2 O.sub.3
--ZrO.sub.2 ceramics;
FIG. 2 is a microstructural photograph of Al.sub.2 O.sub.3 -3 wt. %
ZrO.sub.2 added with 0.2 wt. % CaO+0.2 wt. % SiO.sub.2 sintered at
1,600.degree. C. as a comparative example;
FIG. 3 is a microstructural photograph of Al.sub.2 O.sub.3 -20 wt. %
ZrO.sub.2 added with 0.4 wt. % SrCO.sub.3 +0.3 wt. % SiO.sub.2 sintered at
1,600.degree. C. according to the present invention;
DETAILED DESCRIPTION OF THE INVENTION
Recently, steps toward labor saving, factory automation and production of
more general-purpose products have made much progress in the cutting
processing area. Accordingly, there is a demand for the development of a
tool which satisfy the requirement for a higher reliability under severer
cutting conditions, not only through performance of both continuous and
discontinuous cutting of steel, but also through discontinuous cutting of
cast iron and combination thereof.
The present inventors have discovered the means for converting Al.sub.2
O.sub.3 matrix itself into platelet-shaped grains in place of dispersing
SiC and other whiskers, and achieved the present invention as an
application thereof particularly in the area of sintered ceramics for
cutting tools.
The present inventors have successfully controlled for the first time, the
size of .alpha.-Al.sub.2 O.sub.3 particles to up to ten and several .mu.m
in the longitudinal direction by utilizing controllers which cause grain
growth of .alpha.-Al.sub.2 O.sub.3 grains into platelet-shaped grains,
under the effect of promoters during sintering by adding the promoters
which are added and the controllers are added to a sinter comprising
.alpha.Al.sub.2 O.sub.3 as the matrix. Addition of the promoters without
adding the controllers considerably reduces the strength through abnormal
grain growth of .alpha.-Al.sub.2 O.sub.3 grains. Addition of the
controllers permits control of the size of platelet .alpha.-Al.sub.2
O.sub.3 grains in the longitudinal direction up to ten and several um, and
reduces the strength. The platelet .alpha.-Al.sub.2 O.sub.3 grains inhibit
propagation of cracks through deflection and grain bridging, thereby
permitting remarkable improvement of fracture toughness without decreasing
the strength.
Effective controllers include ZrO.sub.2, HfO.sub.2, partially stabilized
ZrO.sub.2 ; partially stabilized HfO.sub.2, SiC grains, SiC whisker, and
carbides, nitrides and carbonitrides of IVa, Va and VIa group metals.
Now, the mechanism is described below in detail while showing the
manufacturing method for converting .alpha.-Al.sub.2 O.sub.3 grains into
platelet-shaped grains of the invention.
The method of the invention basically comprises the steps of mixing
promoters (from 0.04 to 4 wt. % as converted into oxides) and various
controllers (from 5 to 40 wt. %) with ordinary aluminium oxide powder, and
sintering the mixture at a temperature of at least 1,300.degree. C. at
which a liquid phase is sufficiently generated.
More specifically, addition of the above-mentioned promoters facilitates
generation of the liquid phase in the sintering stage by reacting with
Al.sub.2 O.sub.3 during heating. Al.sub.2 O.sub.3 is dissolved into this
liquid phase, and the dissolved Al.sub.2 O.sub.3 precipitates again on the
surfaces of .alpha.-Al.sub.2 O.sub.3 crystal grains. In the present
invention, the following mechanism formed platelet-shaped grains.
The liquid phase, when produced, reduces the surface energy of the C-plane
((0001) plane) of .alpha.-Al.sub.2 O.sub.3 crystal, thereby stabilizing
this plane.
In order to reduce the energy of the entire .alpha.-Al.sub.2 O.sub.3
grains, the grains must have wide stable planes and unstable planes must
be reduced in area. .alpha.-Al.sub.2 O.sub.3 grains are considered to grow
as the C-plane becomes wider, thus leading to the production of
.alpha.-Al.sub.2 Al.sub.2 O.sub.3 grains.
When .alpha.-Al.sub.2 O.sub.3 grains grow into platelet-shaped grains, the
growth of platelets can be controlled with controllers. The platelets
collide with the controllers: with a slight amount of added controllers,
platelets grow while incorporating the controllers into grains, resulting
in abnormal grain growth of the platelets.
By adding the controllers in an amount of at least 5 wt. %, it was possible
to control the growth of platelets, i.e., the grain size, because the
controllers are mainly distributed at grain boundaries.
In order to produce this mechanism, it is necessary to add from 0.02 to 2%
one or more of oxides of alkali metals such as Li, Na and K and oxides of
alkali earth metals such as Ca, Sr and Ba, and from 0.02 to 2% SiO.sub.2
as the above-mentioned promoters. These additives suffice to be present in
the form of oxides during sintering.
These components may, therefore, be added as oxides from the beginning, but
may, also be added by using salts which are decomposed during sintering
into oxides from salts of chlorides, carbonates, nitrates, sulfates,
oxalates and alkoxides of the above mentioned promoters.
This decomposing reaction may be separated, i.e., the above-mentioned
compounds may be converted into oxides, through a heat treatment at a
temperature ranging from 600.degree. to 1,050.degree. C. before sintering.
After addition, mixing and formation of the controllers, sintering may be
carried out.
The liquid-phase component may be produced by previously mixing the
promoters and Al.sub.2 O.sub.3 powder at a stage prior to the mixing step,
causing a reaction at a high temperature ranging from about 1,000.degree.
to 1,500.degree. C., grinding this provisional sinter of the liquid-phase
component, and mixing this liquid-phase component, .alpha.-Al.sub.2
O.sub.3 and various controlling components before sintering.
The liquid phase produced during sintering is vitrified or crystallized
during cooling after sintering and is present at grain boundaries.
In sintering, the above-mentioned sinter is available by any of the method
of sintering the shape at a temperature of from 1,300.degree. to
1,900.degree. C. in the air or in an inert gas atmosphere or in vacuum,
the method of subjecting the sinter further to an HIP treatment at a
temperature of from 1,300.degree. to 1,700.degree. C. under pressure of
from 100 to 200 MPa, and the method of hot-pressing the mixed powder at a
temperature of from 1,300.degree. to 1,900.degree. C. under a pressure of
from 10 to 40 MPa. Basically any amethod, which permits formation of the
above-mentioned liquid phase. When appropriate, CIP and slip casting may
be employed to manufacture a large-sized products such as a nozzle, a die,
a rolling roll or an engineering ceramics.
Furthermore, wear resistance can be improved with the use of chemical vapor
deposition by coating an object with a single or multiple-phase layer of
solid-solution of one or more of such hard substances as oxides, carbides,
carbonitrides and nitrides of aluminium and IVa, Va and VIa group metals.
Following are a brief description of the constituents of the present
invention.
(a) Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
(promoters)
Effective additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
(promoters) include one or more of oxides of Li, K, Na, Ca, Sr and Ba, and
SiO.sub.2, which react with part of Al.sub.2 O.sub.3, form a liquid phase
during sintering, and cause grain growth of .alpha.-Al.sub.2 O.sub.3
grains into platelet grains. With an amount of each of such promoters of
under 0.02 wt. % (0.04 wt. % in total), platelet .alpha.-Al.sub.2 O.sub.3
grains do not grow because of the small amount of liquid phase. An amount
of over 2 wt. % (4 wt. % in total) is not desirable particularly because
of a decrease in strength and high-temperature hardness.
(b) Components controlling grain growth of .alpha.-Al.sub.2 O.sub.3
platelets (controllers)
Components controlling grain growth of .alpha.-Al.sub.2 O.sub.3 platelets
(controllers) control grain growth of .alpha.-Al.sub.2 O.sub.3 platelets.
Without addition of these components, abnormal grain growth of platelet
.alpha.-Al.sub.2 O.sub.3 grains is caused, resulting in a large decrease
in strength. Even with controllers, a low content of under 5 wt. % causes
.alpha.-Al.sub.2 O.sub.3 grains to grow beyond the controllers. As shown
in the photograph of FIG. 2, for example, representing a case of
.alpha.-Al.sub.2 O.sub.3 wt. % ZrO.sub.2 added with CaO and SiO.sub.2 each
in an amount of 0.2 wt. %, strength is still insufficient since platelet
.alpha.-Al.sub.2 O.sub.3 grains have a size of several tens of .mu.m.
Controllers in amount over 40 wt. % produce in sufficient growth of
.alpha.-Al.sub.2 O.sub.3 grains into platelets and results in a lower
toughness. The controller content should, therefore, preferably be within
a range of from 5 to 40 wt. %. It is also necessary that most of platelet
.alpha.-Al.sub.2 O.sub.3 grains have a longer diameter of up to 15 .mu.m,
to ensure sufficient strength and toughness.
Preferable controllers include ZrO.sub.2 and HfO.sub.2 grains, partially
stabilized ZrO.sub.2 and partially stabilized HfO.sub.2 containing Y.sub.2
O.sub.3, MgO, CaO and CeO.sub.2, SiC whisker, carbides, carbonitrides and
nitrides of IVa, Va and VI group metals, and SiC particles.
(c) Addition of promoters and heat treatment temperature
The controller must be present in the form of oxides during sintering. The
controllers may be added in the form of oxides or in the form of various
salts. More specifically, the promoter may be oxides, chlorides,
carbonates, nitrates and oxalates of Li, K, Na, Ca, Sr and Ba, oxides for
Si, and alkoxide.
A heat treatment temperature of under 600.degree. C. leads to insufficient
decomposition into oxides. With a heat treatment temperature of over
1,050.degree. C., powder particles condense among themselves, which form a
defect after sintering, thus reducing strength of the sinter. The heat
treatment temperature should therefore preferably be within a range of
from 600.degree. to 1,050.degree. C. Al.sub.2 O.sub.3 powder or all or
part of the controllers may previously be mixed with compounds producing
the promoters for the heat treatment.
A similar ceramics is available through preparation of this Al.sub.2
O.sub.3 based ceramics by provisionally sintering a mixed powder of
Al.sub.2 O.sub.3 powder and at least one of oxides, chlorides, carbonates,
nitrates, sulfates and oxalates of Li, K, Na, Ca, Sr and Ba and at least
one of SiO.sub.2 and/or Si alkoxide at a temperature of from 1,000.degree.
to 1,500.degree. C. at which a liquid phase is produced to prepare a
liquid phase component, grinding this liquid-phase component, adding the
ground powder, Al.sub.2 O.sub.3 powder and controllers, mixing the same so
as to achieve a chemical composition comprising from 0.04 to 4 wt. %
promoters, from 5 to 40 wt. % controllers and the balance Al.sub.2
O.sub.3, and sintering the resultant powder shape.
(d) Sintering
The sintering atmosphere may be an oxidizing atmosphere such as air when
using one or more oxides such as ZrO.sub.2 and HfO.sub.2 as the
controllers, and must be an inert atmosphere such as vacuum or argon when
using controllers poor in oxidation resistance (such as SiC, carbides,
carbonitrides and nitrides of IVa, Va and VIa group metals), with a
sintering temperature of under 1,300.degree. C., sintering would be
insufficient, and with a sintering temperature of over 1,900.degree. C.,
excessive growth of .alpha.-Al.sub.2 O.sub.3 grains largely reduces
strength.
It is also possible to densify the product by subjecting the sinter to an
HIP treatment, using an inert gas, at a temperature of from 1,300.degree.
to 1,700.degree. C. under a pressure of from 100 to 200 MPa.
While hot-press sintering is applicable to any material, hot press
sintering is required particularly when using SiC whisker as a controller
because of the low sinterability thereof. A temperature of under
1,300.degree. C. leads to an insufficient sintering, and a temperature of
over 1,900.degree. C. results in excessive growth of .alpha.-Al.sub.2
O.sub.3 grains and hence a considerable decrease in strength. A press
pressure of under 10 MPa leads to insufficient densification, whereas a
pressure of over 40 MPa poses the problem of pressure resistance of the
pressing die. (However, if a die having a high pressure resistance is
developed, no problem would be posed up to the pressure resistance of that
die.)
(e) Coating
When the layer of Al.sub.2 O.sub.3 and carbides, carbonitrides and nitrides
of IVa, Va and VIa group metals has a thickness of under 1 .mu.m, the
effect of improving wear resistance is limited and a layer thickness of
over 20 .mu.m is not desirable because of the easy occurrence of breakage
or chipping.
The following is a brief synopsis of the present invention.
The present invention relates to an Al.sub.2 O.sub.3 based ceramics in
which .alpha.-Al.sub.2 O.sub.3 grains appropriately grow into platelets by
the addition of controllers and promoters, a method of manufacturing the
same, and a ceramics having a coating layer on the surface thereof.
The Al.sub.2 O.sub.3 based ceramic composite comprising platelet
.alpha.-Al.sub.2 O.sub.3 grains comprises substantially:
controllers: from 5 to 40 wt. %,
promoters: from 0.04 to 4 wt. %, and
.alpha.-Al.sub.2 O.sub.3 and incidental impurities; balance.
In the sintering stage thereof, the promoters react with part of Al.sub.2
O.sub.3 to produce a liquid phase which in turn produces platelet
.alpha.-Al.sub.2 O.sub.3 grains. Addition of the controllers permits
control of the growth of platelet .alpha.-Al.sub.2 O.sub.3 grains to up to
15 .mu.m, and thus makes it possible to manufacture an Al.sub.2 O.sub.3
based ceramic composite excellent in both strength and toughness. The
promoters should preferably comprise one or more (from 0.02 to 2 wt. %) of
oxides of Li, K, Na, Ca, Sr and Ba. The controllers comprise one or more
of ZrO.sub.2 powder, HfO.sub.2 powder, partially stabilized ZrO.sub.2
powder, partially stabilized HfO.sub.2 powder, powder of carbides,
nitrides and carbonitrides of IVa, Va and VIa group metals, SiC powder,
and SiC whisker. The coating layer, having a thickness of from 1 to 20
.mu.m, comprises a single or multiple layers of one or more of carbides,
nitrides and carbonitrides of IVa, Va and VIa group metals, and Al.sub.2
O.sub.3.
(EXAMPLE 1)
There were prepared Al.sub.2 O.sub.3 powder having an average particle size
of 0.3 .mu.m as the raw material, powder of various compounds of Li, K,
Ns, Ca, Sr and Be, SiO.sub.2 powder and Si alkoxide, having an average
particle size of from 0.1 to 5 .mu.m as the promoters, and ZrO.sub.2
powder, HfO.sub.2 powder, and partially stabilized ZrO.sub.2 powder and
partially stabilized HfO.sub.2 powder containing Y.sub.2 O.sub.3 and
CeO.sub.2, having an average particle size of from 0.1 to 1 .mu.m, as the
controllers. First, the promoters were blended into Al.sub.2 O.sub.3
powder at a ratios as shown in Table 1 (ratio to the overall mixture), and
mixed for 72 hours on a ball mill. Then a heat treatment was applied under
conditions as shown in Table 2 in the open air. Then, the controllers were
blended at a ratio as shown in Table 1 (ratio to the overall mixture) and
the blend was mixed on a ball mill for 72 hours and dried to obtain a
mixed powder. The mixed powder was press-formed under a pressure of 1
ton/cm.sup.2, and the formed mixture was sintered for one hour at a
temperature as shown in Table 2, thereby preparing Al.sub.2 O.sub.3
--ZrO.sub.2 based ceramic samples of the present invention.
For comparison purposes, furthermore, conventional Al.sub.2 O.sub.3
--ZrO.sub.2 based ceramics were prepared, by using the above-mentioned
Al.sub.2 O.sub.3 powder. ZrO.sub.2 powder, HfO.sub.2 powder, and partially
stabilized ZrO.sub.2 powder and partially stabilized HfO.sub.2 powder
containing Y.sub.2 O.sub.3 and CeO.sub.2 as raw material powders, and
blending these raw material powders at a blending ratio as shown in Table
1, under the same conditions as above except that no heat treatment was
conducted and sintering was carried out at a temperature shown in Table 2.
For the resultant samples of ceramics, a discontinuous cutting test of
steel was carried out under conditions:
Material to be cut: SCM440 (hardness: HB250) round bar with two
longitudinal grooves,
Tool geometry: JIS SNGN120408,
Cutting speed: 400 m/min,
Depth of cut: 1 mm,
Feed: 0.15 mm/rev., and
Wet cutting time: 15 minutes,
and a continuous cutting test of steel was conducted under conditions:
TABLE 1
__________________________________________________________________________
Blending composition (% by weight)
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet
Components controlling the
grain
Li, K, Na, Ca, Sr, Ba-compounds
Si-compounds growth of .alpha.-Al.sub.2
O.sub.3 platelets
Convert Unstabilized and partially
stabilized
Amount into oxide
Amount Convert into oxide
ZrO.sub.2 /HfO.sub.2
Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics of
present
invention
1 BaCO.sub.3 : 0.5
0.33 Si(OCH.sub.3).sub.4 : 0.5
0.20 ZrO.sub.2 (Y.sub.2 O.sub.3 : 2
mol %): 20 Remainder
2 SrCO.sub.3 : 0.4
0.23 SiO.sub.2 : 0.3
0.30 ZrO.sub.2 : 20 Remainder
3 Ba(NO.sub.3).sub.2 : 1
0.59 SiO.sub.2 : 0.2
0.20 HfO.sub.2 : 15 Remainder
4 CaO: 0.2 0.20 Si(OC.sub.2 H.sub.5).sub.4 :
0.21 ZrO.sub.2 : 20 Remainder
0.4
Si(OC.sub.3 H.sub.7).sub.4 :
0.4
5 BaCl.sub.2 : 2.7
2.00 SiO.sub.2 : 1.5
1.50 ZrO.sub.2 (Y.sub.2 O.sub.3 : 2
mol %): 15 Remainder
6 BaCO.sub.3 : 0.3, SrO: 1.0
1.23 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 (CeO.sub.2 : 12 mol
%): 20 Remainder
7 SrCO.sub.3 : 0.2, BaCl.sub.2 : 0.2
0.26 SiO.sub.2 : 0.1
0.21 ZrO.sub.2 : 15 Remainder
Si(OC.sub.2 H.sub.5).sub.4 :
ZrO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 5
0.5
8 SrCO.sub.3 : 0.2, BaCl.sub.2 : 0.2
0.32 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 : 20 Remainder
Ca(NO.sub.3).sub.2 : 0.1 ZrO.sub.2 : 25
9 CaCO.sub.3 : 0.1, SrO: 0.1,
0.26 SiO.sub.2 : 0.3
0.30 ZrO.sub.2 : 25 Remainder
BaCl.sub.2 : 0.2
Ba(NO.sub.3).sub.2 0.1
10 BaCO.sub.3 : 0.6
0.47 SiO.sub.2 : 0.3
0.30 ZrO.sub.2 : 5 Remainder
11 SrCO.sub.3 : 0.4
0.28 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 40 Remainder
12 NaCO.sub.3 : 0.1, SrCO.sub.3 : 0.3
0.27 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 : 20 Remainder
13 LiNO.sub.3 : 0.09
0.02 SiO.sub.2 : 0.2
0.20 HfO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 20 Remainder
14 BaSO.sub.4 : 0.2, CaCO.sub.3 : 0.2
0.24 SiO.sub.2 : 0.3
0.30 HfO.sub.2 : 5, ZrO.sub.2 :
Remainder
15 BaC.sub.2 O.sub.4 H.sub.2 O: 0.4
0.25 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 : 20 Remainder
Conventional
ceramics
1 -- -- -- -- ZrO.sub.2 (CeO.sub.2 : 10 mol
%): 5 Remainder
2 -- -- -- -- ZrO.sub.2 : 20 Remainder
3 -- -- -- -- ZrO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 40 Remainder
4 -- -- -- -- HfO.sub.2 : 20 Remainder
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
Heat treatment
Sintering
Flank wear .alpha.-Al.sub.2 O.sub.3
grain Bending
Fracture
Temperature
Time
temperature
(mm) morphology
strength
toughness
(.degree.C.)
(Hr)
(.degree.C.)
Interrupt
Continuous
Shape
Size (.mu.m)
(MPa)
(MPa
__________________________________________________________________________
m.sup.1/2)
Ceramics of present invention
1 800 1 1600 0.23 0.20 Platelet
4 700 6.0
2 800 1 1600 0.22 0.18 Platelet
3 710 6.2
3 800 1 1600 0.26 0.17 Platelet
6 800 5.6
4 600 1 1500 0.25 0.21 Platelet
2 1000
5.2
5 900 1 1700 0.31 0.29 Platelet
10 860 5.2
6 800 1 1600 0.28 0.24 Platelet
4 800 5.3
7 900 1 1600 0.27 0.21 Platelet
4 800 5.3
8 800 1 1600 0.25 0.21 Platelet
3 710 5.8
9 800 1 1500 0.24 0.18 Platelet
2 850 6.0
10 900 2 1500 0.27 0.26 Platelet
3 780 5.2
11 800 1 1600 0.24 0.22 Platelet
2 850 5.0
12 650 1 1450 0.24 0.23 Platelet
2 700 5.3
13 700 1 1300 0.26 0.24 Platelet
2 680 5.2
14 800 1 1700 0.24 0.25 Platelet
15 800 5.8
15 1000 2 1600 0.25 0.24 Platelet
4 750 5.6
Conventional
ceramics
1 -- -- 1500 Fractured in 2 min.
0.24 Equiaxed
2 450 3.2
4 -- -- 1600 Fractured in 7 min.
0.19 Equiaxed
2 600 4.3
5 -- -- 1600 Fractured in 3 min.
0.19 Equiaxed
1 800 4.5
6 -- -- 1600 Fractured in 5 min.
0.21 Equiaxed
3 650 4.3
__________________________________________________________________________
Material to be cut: SCM440 (hardness: HB250) round bar,
Tool geometry: JIS SNGN120408,
Cutting speed: 300 m/min,
Depth of cut: 1.5 mm,
Feed: 0.2 mm/rev., and
Wet cutting time: 10 minutes.
The worn width on the relief face of the cutting edge was measured in the
both tests. The results of tests are shown in Table 2. Table 2 also shows
the shape, particle size, bending strength and fracture toughness of
.alpha.-Al.sub.2 O.sub.3 grains.
FIGS. 1 and 3 respectively show structural photographs of the conventional
ceramics 2 and the ceramics 2 of the present invention 2 based on a
scanning-type electron microscope.
As shown in FIGS. 1 and 3, while the samples of the invention exhibit a
mixed structure mainly comprising platelet Al.sub.2 O.sub.3 crystal grains
(gray) and equiaxed ZrO.sub.2 crystal grains (white), the conventional
samples demonstrate a mixed structure of equiaxed Al.sub.2 O.sub.3 and
equiaxed ZrO.sub.2 crystal grains, thus clearly revealing the difference
in structure between these samples. This structural difference is
reflected in toughness: as shown in Table 2, the samples of the invention
have a far superior toughness to the conventional ones. Accordingly,
although these groups of samples show similar cutting properties in
continuous cutting of steel, in discontinuous cutting of steel, all the
conventional samples suffered damages to the cutting edge with a
relatively short service life, whereas the samples of the invention were
free from occurrence of breakage or chipping in the cutting edge and
displayed an excellent wear resistance for a along period of time.
(EXAMPLE 2)
Mixed powders were obtained by using the same raw materials as in the
Example 1, blending these raw materials at a ratio shown in Table 3.
mixing the same on a ball mill for 72 hours and drying the same. Al.sub.2
O.sub.3 --ZrO.sub.2 based ceramic samples of the present invention were
prepared by press-forming the mixed powders under a pressure of 1
ton/cm.sup.2 and sintering the formed powders in the open air for one hour
at a temperature show in Table 4.
For comparison purposes, conventional Al.sub.2 O.sub.3 --ZrO.sub.2 based
ceramic samples were prepared in the same manner as in Example 1.
For the resulting samples of ceramics, cutting tests were carried out under
the same conditions as in the Example 1. The results are shown in Table 4.
The shape, particle size, bending strength and fracture toughness of
.alpha.-Al.sub.2 O.sub.3 grains are also shown in Table 4.
As shown in Table 4, the samples of the invention have a far superior
toughness to that of the conventional samples. Accordingly, although these
groups of samples show similar cutting properties in continuous cutting of
steel, in discontinuous cutting of steel, all the conventional samples
suffered damages to the cutting edge with a relatively short service life,
whereas the samples of the invention were free from of breakage or
chipping in the cutting edge and displayed an excellent wear resistance
for a long period of time.
(EXAMPLE 3)
There were prepared Al.sub.2 O.sub.3 powder, having an average particle
size of 0.3 .mu.m as the raw material, powder of various compounds of Li,
K, Ns, Ca, Sr and Be, SiO.sub.2 powder and Si alkoxide, having an average
particle size of from 0.1 to 5 .mu.m as the promoters, and ZrO.sub.2
powder, HfO.sub.2 powder, partially stabilized ZrO.sub.2 powder and
partially stabilized HfO.sub.2 powder containing Y.sub.2 O.sub.3 and
CeO.sub.2, carbide powder, nitride powder, and carbonitride powder of IVa,
Va and VIa
TABLE 3
__________________________________________________________________________
Blending composition (% by weight)
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet
Components controlling the grain
growth of
Li, K, Na, Ca, Sr, Ba-compounds
SiO.sub.2
.alpha.-Al.sub.2 O.sub.3 platelets
Convert Convert
Unstabilized and partially
stabilized
Amount into oxide
Amount
into oxide
ZrO.sub.2 /HfO.sub.2
Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics of
present invention
1 CaCO.sub.3 : 0.05
0.02 0.02
0.02 ZrO.sub.2 : 10 Remainder
2 BaO: 2 2.00 1.5 1.50 ZrO.sub.2 : 15 Remainder
3 SiO: 0.3 0.30 0.2 0.20 HfO.sub.2 : 15 Remainder
4 CaCO.sub.3 : 0.1, Ca(NO.sub.3).sub.2 : 0.1
0.09 0.2 0.20 ZrO.sub.2 : 10, HfO.sub.2 :
Remainder
5 BaO: 0.2, CaCl.sub.2 : 0.1
0.25 0.2 0.20 HfO.sub.2 : 20 Remainder
6 CaCO.sub.3 : 0.1, CaO: 0.1, Ca(NO.sub.3).sub.2 :
0.19 0.1 0.10 ZrO.sub.2 : 25 Remainder
7 K.sub.2 SO.sub.4 : 0.1
0.05 0.3 0.30 ZrO.sub.2 : 5 Remainder
8 Li.sub.2 NO.sub.3 : 0.1, Na.sub.2 SO.sub.4 : 0.1
0.07 0.1 0.10 ZrO.sub.2 (CeO.sub.2 : 12 mol %):
30 Remainder
9 Na.sub.2 CO.sub.3 : 0.1
0.06 0.1 0.10 ZrO.sub.2 (Y.sub.2 O.sub.3 : 3 mol
%): 20 Remainder
__________________________________________________________________________
TABLE 4
__________________________________________________________________________
Sintering
Flank wear .alpha.-Al.sub.2 O.sub.3 grain
Bending
Fracture
temperature
(mm) molphology
strength
toughness
(.degree.C.)
Interrupt
Continuous
Shape
Size (.mu.m)
(MPa)
(MPa m.sup.1/2)
__________________________________________________________________________
Ceramics of present invention
1 1600 0.30 0.22 Platelet
4 790 5.7
2 1600 0.26 0.29 Platelet
4 810 5.5
3 1600 0.28 0.17 Platelet
4 820 5.3
4 1600 0.24 0.20 Platelet
3 710 5.6
5 1500 0.24 0.19 Platelet
4 1050
5.7
6 1500 0.22 0.20 Platelet
2 950 5.4
7 1400 0.27 0.28 Piatelet
10 700 5.0
8 1600 0.24 0.27 Platelet
3 760 5.5
9 1300 0.24 0.26 Platelet
4 730 5.2
__________________________________________________________________________
group metals, having an average particle size of from 0.1 to 1 .mu.m, as
the controllers. First, the controllers were blended into Al O powder at a
ratio as shown in Table 5 (ratio to the overall mixture)1, and mixed for
72 hours on a ball mill. Then, a heat treatment was applied under
conditioned as shown in Table 6 in the open air. Then, the controllers
were blended at a ratio as shown in Table 5 (ratio to the overall
mixture), and the blend was mixed on a ball mill for 72 hours and dried to
obtain a mixed powder. The mixed powder was press-formed under a pressure
of 1 ton/cm, and the formed mixture was sintered in an inert gas
atmosphere for one hour at a temperature as shown in Table 6. In addition,
an HIP treatment was conducted in argon gas at 1,500.degree. C. under a
pressure of 150 MPa for an hour, thereby preparing Al.sub.2 O.sub.3 based
ceramic composite of the present invention.
For comparison purposes, furthermore, conventional Al.sub.2 O.sub.3 based
ceramic composite were prepared, by using the above-mentioned ZrO.sub.2
powder, HfO.sub.2 powder, partially stabilized ZrO.sub.2 powder and
partially stabilized HfO.sub.2 powder containing Y.sub.2 O.sub.3 and
CeO.sub.2, carbide powder, nitride powder and carbonitride powder of IVa,
Va and VIa group metals, SiC powder and Al.sub.2 O.sub.3 powder as raw
material powders, blending these material powders as a blending ratio as
shown in Table 5, sintering the same without applying a heat treatment
under conditions as shown in Table 6, and carrying out an HIP treatment
under the same conditions.
For the resultant samples of ceramics, a continuous cutting test of steel
was carried out under conditions:
Material to be cut: SCM440 (hardness: HB250) round bar,
Tool geometry: JIS SNGN 120408
Cutting speed: 350 m/min,
Depth of cut: 1 mm,
Feed: 0.2 mm/rev., and
Wet cutting time: 10 minutes,
TABLE 5
__________________________________________________________________________
Blending composition (% by weight)
Components controlling the grain
growth of
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
.alpha.-Al.sub.2 O.sub.3 platelets
Li, K, Na, Ca, Sr, Ba-compounds
Si-compounds Unstabilized and
Convert Convert
partially stabilized
IVa, Va, VIa metal
Amount into oxide
Amount into oxide
ZrO.sub.2 /HfO.sub.2
compounds and
Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics of
present
invention
1 BaCO.sub.3 : 0.5
0.39 SiO.sub.2 : O.3
0.30 ZrO.sub.2 (Y.sub.2 O.sub.3 : 3 mol
%): 15 TiCN: 10 Remainder
2 Ba(NO.sub.3).sub.2 : 1
0.59 Si(OC.sub.3 H.sub.7).sub.4 : 0.7
0.16 ZrO.sub.2 : 20
TiC: 5 Remainder
3 CaO: 0.2 0.20 Si(OC.sub.2 H.sub.5).sub.4 : 0.7
0.20 ZrO.sub.2 : 10
WC: 8 Remainder
4 BaO: 2.0 2.00 SiO.sub.2 : 2
2.00 HfO.sub.2 : 10
TiCN: 10 Remainder
5 BaCO.sub.3 : 0.4, Ba(NO.sub.3).sub.2 : 0.2
0.43 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 : 20
TiC: 10, TiN:
Remainder
6 SrCO.sub.3 : 0.2, CaO: 0.1
0.24 SiO.sub.2 : 0.4
0.40 ZrO.sub.2 : 10
ZrCN: 10 Remainder
7 Na.sub.2 CO.sub.3 : 0.5
0.29 SiO.sub.2 : 0.4
0.40 HfO.sub.2 : 10
TiCN: 10 Remainder
8 K.sub.2 SO.sub.4 : 0.4, SrCO.sub.3 : 0.1
0.29 SiO.sub.2 : 0.4
0.40 ZrO.sub.2 (CeO.sub.2 : 12 mol %):
TiN: 20 Remainder
9 SrCO.sub.3 : 0.5
0.35 SiO.sub.2 : 0.5
0.50 -- SiC: 20 Remainder
10 BaC.sub.2 O.sub.4 H.sub.2 O: 0.4
0.25 SiO.sub.2 : 0.2
0.20 ZrO.sub.2 : 10
TiCN: 20 Remainder
11 CaCO.sub.3 : 0.3
0.17 SiO.sub.2 : 0.2
0.20 -- ZrCN: 25 Remainder
12 CaO: 0.3 0.30 SiO.sub.2 : 0.2
0.20 -- TaC: 20 Remainder
13 LiNO.sub.3 : 0.2
0.04 SiO.sub.2 : 0.03
0.03 ZrO.sub.2 : 10
TiCN: 10, SiC:
Remainder
14 K.sub.2 SO.sub.4 : 0.1, Na.sub.2 SO.sub.4 : 0.1
0.09 SiO.sub.2 : 0.3
0.30 -- TiCN: 5 Remainder
Conventional
ceramics
1 -- -- -- -- ZrO.sub.2 : 10
TiC: 10 Remainder
2 -- -- -- -- ZrO.sub.2 (Y.sub.2 O.sub.3 : 2 mol
%): 15 TiN: 10 Remainder
3 -- -- -- -- HfO.sub.2 : 10
SiC: 10 Remainder
4 -- -- -- -- ZrO.sub.2 : 15
TiN: 5, TiCN:
Remainder
SiC: 5
5 -- -- -- -- -- TiCN: 30 Remainder
6 -- -- -- -- -- ZrC: 15 Remainder
__________________________________________________________________________
TABLE 6
__________________________________________________________________________
Heat treatment
Sintering
Flank .alpha.-Al.sub.2 O.sub.3
Bending
Fracture
Temperature
Time
temperature
wear morphology
strength
toughness
(.degree.C.)
(Hr)
(.degree.C.)
(mm) Shape
Size (.mu.m)
(MPa)
(MPa
__________________________________________________________________________
m.sup.1/2)
Ceramics of present invention
1 800 1 1800 0.32 Platelet
4 800 5.5
2 800 1 1650 0.29 Platelet
2 800 6.5
3 600 2 1700 0.28 Platelet
4 750 5.3
4 700 1 1700 0.34 Platelet
4 710 6.0
5 900 1 1700 0.30 Platelet
2 850 6.4
6 800 1 1900 0.32 Platelet
7 740 5.1
7 700 1 1600 0.32 Platelet
3 720 5.5
8 800 2 1650 0.34 Platelet
1 780 5.7
9 800 1 1750 0.33 Platelet
2 750 5.1
10 1050 1 1650 0.29 Platelet
1 800 6.0
11 700 1 1850 0.31 Platelet
2 750 5.2
12 600 1 1850 0.32 Platelet
2 760 5.0
13 700 1 1750 0.32 Platelet
1 740 5.3
14 800 1 1700 0.33 Platelet
13 780 5.4
Conventional
ceramics
1 -- -- 1850 Fractured in 5 min.
Equiaxed
3 700 3 8
2 -- -- 1850 Fractured in 4 min.
Equiaxed
3 760 3.8
3 -- -- 1850 Fractured in 6 min.
Equiaxed
2 720 4.2
4 -- -- 1800 Fractured in 6 min.
Equiaxed
1 720 4.0
5 -- -- 1750 Fractured in 3 min.
Equiaxed
1 700 3.5
6 -- -- 1700 Fractured in 4 min.
Equiaxed
2 720 4.2
__________________________________________________________________________
and the worn width of the relief face of the cutting edge was measured. The
results are shown in Table 6. Table 6 also shows the shape, particle size,
bending strength and fracture toughness of .alpha.-Al.sub.2 O.sub.3
grains.
As shown in Table 6, the ceramics of the present invention, having a
structure in which Al.sub.2 O.sub.3 grains have grown into platelets, are
clearly superior in toughness, and this is reflected in the fact that the
ceramics of the present invention are free from breakage or chipping in
continuous cutting of steel and display excellent wear resistance for a
long period of time.
(EXAMPLE 4)
There were prepared Al.sub.2 O.sub.3 a powder, having an average particle
size of 0.3 .mu.m, as the raw material, powder of various compounds of Li,
K, Na, Ca, Sr and Ba, SiO.sub.2 powder and Si alkoxide, having an average
particle size of from 0.1 to 5 .mu.m, as the promoters, and SiC whisker
containing at least 70% whiskers of an aspect ratio of from 35 to 40 with
a length of from 15 to 50.mu.m and a diameter of from 0.4 to 2 .mu.m, as
the controllers. First, the promoters were blended into Al.sub.2 O.sub.3
powder at a ratio as shown in Table 7 (ratio to the overall mixture), and
the mixture was mixed for 72 hours on a ball mill. Then, a heat treatment
was applied in the air under conditions as shown in Table 8, and the
head-treated mixture was converted into slurry on a wet ball mill. Then,
SiC whisker was blended at a ratio shown in Table 7 (ratio to the overall
mixture), and wet-mixed for two hours by means of ultrasonic waves and
mechanical mixture. After drying, the mixture was hot-pressed under
conditions shown in Table 8, thereby preparing an Al.sub.2 O.sub.3 based
ceramic composite of the present invention.
For comparison purposes, furthermore, conventional Al.sub.2 O.sub.3 based
ceramic composites were prepared by using the above-mentioned Al.sub.2
O.sub.3 powder and SiC whisker, mixing these raw material powders
TABLE 7
__________________________________________________________________________
Blending composition (% by weight)
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
Li, K, Na, Ca, Sr, Ba-compounds Components controlling the
grain
Convert
Si-compounds growth of .alpha.-Al.sub.2
O.sub.3 platelets
into Convert
SiC
Amount oxide
Amount into oxide
whisker Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics of
present
invention
1 CaCO.sub.3 : 0.05
0.02
Si(OC.sub.2 H.sub.5).sub.4 : 0.4
0.05 5 Remainder
2 BaCO.sub.3 : 0.5
0.39
SiO.sub.2 : 0.2
0.20 10 Remainder
3 SrCO.sub.3 : 0.4
0.28
SiO.sub.2 : 0.3
0.30 15 Remainder
4 Ca(NO.sub.3).sub.2 : 0.15
0.05
SiO.sub.2 : 0.02
0.02 20 Remainder
5 CaCl.sub.2 : 0.5
0.25
SiO.sub.2 : 0.1, Si(OC.sub.3 H.sub.7).sub.4 :
0.3 0.17 20 Remainder
6 BaO: 2 2.00
SiO.sub.2 : 2
2.00 30 Remainder
7 SrO: 1 1.00
SiO.sub.2 : 1.0
1.00 20 Remainder
8 BaCO.sub.3 : 0.4, SrCl.sub.2 : 0.2
0.44
SiO.sub.2 : 0.2
0.20 35 Remainder
9 SrCO.sub.3 : 0.1, CaO: 0.1, Ba(NO.sub.3).sub.2 : 0.1
0.23
SiO.sub.2 : 0.2
0.20 25 Remainder
10 K.sub.2 SO.sub.4 : 0.1
0.05
SiO.sub.2 : 0.2
0.20 25 Remainder
11 Na.sub.2 CO.sub.3 : 0.1, SrCO.sub.3 : 0.1
0.13
SiO.sub.2 : 0.2
0.20 20 Remainder
12 LiNO.sub.3 : 0.1
0.02
SiO.sub.2 : 0.1
0.10 25 Remainder
13 BaC.sub.2 O.sub.4 H.sub.2 O: 2
1.26
SiO.sub.2 : 1.0
1.00 40 Remainder
14 NaNO.sub.3 : 0.5
0.18
SiO.sub.2 : 0.2
0.20 25 Remainder
15 LiNO.sub.3 : 0.05, NaNO.sub.3 : 0.05
0.03
SiO.sub.2 : 0.1
0.10 25 Remainder
Conventional
ceramics
1 -- -- -- -- 5 Remainder
2 -- -- -- -- 17 Remainder
3 -- -- -- -- 30 Remainder
4 -- -- -- -- 40 Remainder
__________________________________________________________________________
TABLE 8
__________________________________________________________________________
Heat treatment
Hot pressing Flank .alpha.-Al.sub.2 O.sub.3
grain Bending
Fracture
Temperature
Time
Temperature
Pressure
Time
wear morphology
strength
toughness
(.degree.C.)
(Hr)
(.degree.C.)
(MPa)
(Hr)
(mm) Shape
Size (.mu.m)
(MPa)
(MPa
__________________________________________________________________________
m.sup.1/2)
Ceramics of present invention
1 800 1 1550 30 1 0.31 Platelet
13 760 6.6
2 800 1 1700 30 1 0.32 Platelet
10 800 7.3
3 800 1 1750 30 1 0 28 Platelet
7 820 7.0
4 900 1 1750 30 1 0.31 Platelet
5 800 7.2
5 800 1 1800 30 1 0.32 Platelet
4 820 7.2
6 1000 2 1850 30 2 0.34 Platelet
2 880 7.5
7 800 1 1750 30 1 0,34 Platelet
2 800 7.2
8 800 1 1800 30 2 0.30 Platelet
2 750 7.4
9 800 1 1700 30 2 0.28 Platelet
3 840 7.2
10 800 1 1950 40 1 0.30 Platelet
3 780 7.2
11 800 1 1700 20 1 0.31 Platelet
5 790 7.3
12 800 2 1950 30 1 0.29 Platelet
4 820 7.5
13 800 1 1750 30 1 0.32 Platelet
2 800 7.5
14 700 1 1750 30 1 0.30 Platelet
3 800 7.6
15 800 1 1750 30 1 0.33 Platelet
3 850 7.5
Conventional
ceramics
1 -- -- 1750 30 1 Fractured in 10 min.
Equiaxed
10 750 5.0
2 -- -- 1750 30 2 Fractured in 12 min.
Equiaxed
5 780 5.5
3 -- -- 1750 30 2 Fractured in 18 min.
Equiaxed
3 800 6.0
4 -- -- 1750 40 2 Fractured in 16 min.
Equiaxed
2 720 6.5
__________________________________________________________________________
under the same conditions so as to achieve the blending composition as
shown in Table 7, and hot-pressing the mixture under conditions as shown
in Table 8, thereby preparing conventional Al.sub.2 O.sub.3 based ceramic
composites.
Subsequently, a milling test of cast iron was carried out on the thus
obtained samples of various ceramics under conditions:
Material to be cut: FC30 (hardness: HB220),
Tool geometry: JIS SNGN 120408,
Cutting speed: 300 m/min,
Depth of cut: 1 mm,
Feed: 0.2 mm/rev., and
Wet cutting time: 20 minutes,
and the worn width of the relief face of the cutting edge was measured. The
results are shown in Table 8. The shape, particle size, bending strength
and fracture toughness; of .alpha.-Al.sub.2 O.sub.3 grains are also shown
in Table 8.
As is clear from Table 8, the ceramics of the present invention, having a
structure in which Al.sub.2 O.sub.3 a grains have grown into platelets,
have a strength of the same order as that of the conventional ceramics,
but are superior in toughness, and this is reflected in the fact that the
ceramics of the present invention are free of breakage or shipping in
discontinuous cutting of cast iron and display excellent wear resistance
for a long period of time.
(EXAMPLE 5)
There were prepared Al.sub.2 O.sub.3 powder, having an average particle
size of 0.3 um, as the raw material, powder of various compounds of Li, K,
Na, Ca, Sr and Be, SiO.sub.2 powder, and Si alkoxide, having an average
particle size of from 0.1 to 5 .mu.m, as the promoters, and ZrO.sub.2
powder, HfO.sub.2 powder, partially stabilized ZrO.sub.2 powder and
partially stabilized HfO.sub.2 powder containing Y.sub.2 O.sub.3 and
CeO.sub.2, having an average particle size of from 0.1 to 12 .mu.m, and
SiC whisker, having a length of from 15 to 59 .mu.m and a diameter of from
0.4 to 2 .mu.m and containing at least 70% whiskers of an aspect ratio of
from 35 to 40 as the controllers. Samples of the Al.sub.2 O.sub.3 based
ceramic composite of the present invention were prepared by first blending
the promoters into Al.sub.2 O.sub.3 powder at a ratio shown in Table 9
(ratio to the overall mixture), mixing the same on a ball mill for 72
hours, then carrying out a heat treatment in the air under conditions as
shown in Table 10, then blending ZrO.sub.2 powder, HfO.sub.2 powder, and
partially stabilized ZrO.sub.2 powder and partially stabilized HfO.sub.2
powder containing Y.sub.2 O.sub.3 and CeO.sub.2 into the heat-treated
mixture, mixing the same on a wet ball mill for 24 hours into slurry,
blending SiC whisker at a ratio shown in Table 9, wet-mixing the same for
two hours by means of ultrasonic waves and mechanical mixing, and after
drying, hot-pressing the same under conditions as shown in Table 10.
For comparison purposes, furthermore, samples of the conventional Al.sub.2
O.sub.3 based ceramic composite were prepared by using the above-mentioned
Al.sub.2 O.sub.3 powder, ZrO.sub.2 powder, HfO.sub.2 powder, partially
stabilized ZrO.sub.2 powder and partially stabilized HfO.sub.2 powder
containing Y.sub.2 O.sub.3 and CeO.sub.2, and SiC whisker as the raw
material powders, mixing these raw material powders under the same
conditions so as to achieve a blended composition as shown in Table 9, and
hot-pressing the blend under conditions as shown in Table 10 without
applying a heat treatment.
Subsequently, a cast iron milling test was carried out under the same
conditions as in the Example 4 for the thus obtained samples of the
various ceramics. The results are shown in Table 10. The shape, particle
size, bending strength and fracture toughness of .alpha.-Al.sub.2 O.sub.3
grains are also shown in Table 10.
As is clear from Table 10, the ceramics of the present
invention, having a structure in which Al.sub.2 O.sub.3 grains have grown
into platelets, have a strength of the same order as that of the
conventional ceramics, but are superior in toughness, and this is
reflected in the fact that the ceramics of the present invention are free
from occurrence of breakage or chipping in wet milling of cast iron and
display excellent wear resistance for a long period of time.
TABLE 9
__________________________________________________________________________
Blending composition (% by weight)
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
Si-compounds Components controlling the
grain
Li, K, Na, Ca, Sr, Ba-compounds Convert
growth of .alpha.-Al.sub.2
O.sub.3 platelets
Convert into
Unstabilized and
SiCtially
Amount into oxide
Amount oxide
stabilized ZrO.sub.2 /HfO.sub.2
whisker
Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics of
present
invention
1 CaCO.sub.3 : 0.05
0.02 SiO.sub.2 : 0.02
0.02
ZrO.sub.2 : 5
30 Remainder
2 SrCO.sub.3 : 0.4
0.28 Si(OC.sub.2 H.sub.5): 4: 0.5
0.14
ZrO.sub.2 (Y.sub.2 O.sub.3 :
2mol %): 30 5 Remainder
3 Ba(NO.sub.3).sub.2 : 0.4
0.23 SiO.sub.2 : 0.1,
0.17
ZrO.sub.2 : 10
20 Remainder
Si(OCH.sub.3).sub.4 : 0.1
ZrO.sub.2 (Y.sub.2 O.sub.3 : 2
mol %): 5
Si(OC.sub.2 H.sub.5).sub.4 : 0.1
4 BaCl.sub.2 : 0.7
0.52 SiO.sub.2 : 0.5
0.50
ZrO.sub.2 (CeO.sub.2 : 12 mol
%): 10 20 Remainder
ZrO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 10
5 SrCl.sub.2 : 0.5
0.33 SiO.sub.2 : 0.2
0.20
ZrO.sub.2 : 15
25 Remainder
6 BaO: 1 1.00 SiO.sub.2 : 1.0
1.00
ZrO.sub.2 : 15
25 Remainder
7 SrO: 1 1.00 SiO.sub.2 : 1.0
1.00
ZrO.sub.2 : 5
25 Remainder
8 BaCO.sub.3 : 2.0, CaO: 0.4
2.00 SiO.sub.2 : 2.0
2.00
HfO.sub.2 : 15
25 Remainder
9 SrCO.sub.3 : 0.1, Sr(NO.sub.3).sub.2 : 0.1, SrCl.sub.2 :
0.18 SiO.sub.2 : 0.3
0.30
ZrO.sub.2 : 10
25 Remainder
10 Na.sub.2 CO.sub.3 : 0.1
0.06 SiO.sub.2 : 0.1
0.10
ZrO.sub.2 : 15
25 Remainder
11 LiNO.sub.3 : 0.2
0.04 SiO.sub.2 : 0.05
0.05
ZrO.sub.2 : 15
20 Remainder
12 K.sub.2 SO.sub.4 : 0.1, SrCO.sub.3 : 0.1
0.12 SiO.sub.2 : 0.2
0.20
HfO.sub.2 : 20
15 Remainder
13 BaC.sub.2 O.sub.4 H.sub.2 O: 1.0
0.63 SiO.sub.2 : 1.0
1.00
ZrO.sub.2 : 15
25 Remainder
14 Li.sub.2 SO.sub.4 : 0.1, Na.sub.2 SO.sub.4 : 0.05
0.06 SiO.sub.2 : 0.05
0.05
ZrO.sub.2 (Y.sub.2 O.sub.3 : 3
mol %): 15 25 Remainder
Conventional
ceramics
1 -- -- -- -- ZrO.sub.2 : 5
30 Remainder
2 -- -- -- -- ZrO.sub.2 (Y.sub.2 O.sub.3 : 2
mol %): 30 5 Remainder
3 -- -- -- -- HFO.sub.2 : 15
15 Remainder
4 -- -- -- -- ZrO.sub.2 (CeO.sub.2 : 12 mol
%): 15 15 Remainder
__________________________________________________________________________
TABLE 10
__________________________________________________________________________
Heat treatment
Hot pressing Flank .alpha.-Al.sub.2 O.sub.3
grain Bending
Fracture
Temperature
Time
Temperature
Pressure
Time
wear morphology
strength
toughness
(.degree.C.)
(Hr)
(.degree.C.)
(MPa)
(Hr)
(mm) Shape
Size (.mu.m)
(MPa)
(MPa
__________________________________________________________________________
m.sup.1/2)
Ceramics of present invention
1 800 1 1850 30 2 0.36 Platelet
2 870 7.1
2 800 1 1650 30 2 0.34 Platelet
2 850 7.2
3 800 1 1700 30 2 0.32 Platelet
2 890 7.4
4 900 1 1700 20 2 0.36 Platelet
2 820 7.2
5 600 1 1700 30 2 0.37 Platelet
2 840 7.6
6 800 1 1700 30 2 0.31 Platelet
1 870 7.1
7 600 1 1700 40 2 0.31 Platelet
3 870 7.5
8 1000 2 1700 30 2 0.31 Platelet
1 800 7.1
9 800 1 1750 30 2 0.30 Platelet
2 850 7.2
10 800 1 1750 30 1 0.32 Platelet
1 870 7.5
11 800 1 1800 30 2 0.33 Platclet
1 850 7.3
12 800 1 1600 30 1 0.35 Platelet
2 930 7.1
13 900 2 1700 30 1 0,32 Platelet
1 880 7.2
14 900 1 1700 30 1 0.34 Platelet
1 870 7.0
Conventional
ceramics
1 -- -- 1750 30 2 Fractured in 17 min.
Equiaxed
2 820 6.0
2 -- -- 1750 30 2 Fractured in 8 min.
Equiaxed
1 840 5.5
3 -- -- 1750 30 2 Fractured in 11 min.
Equiaxed
2 810 5.9
4 -- -- 1750 30 2 Fractured in 12 min.
Equiaxed
2 830 6.0
__________________________________________________________________________
(EXAMPLE 6)
There were prepared Al.sub.2 O.sub.3 powder, having an average particle
size of 0.3 .mu.m; as the raw material, powders of various compounds of
Li, K, Ns, Ca, Sr and Be, SiO.sub.2 powder, and Si alkoxide, having an
average particle size of from 0.1 to 5 .mu.m, as the promoters, and
ZrO.sub.2 powder, HfO.sub.2 powder, partially stabilized ZrO.sub.2 and
partially stabilized HfO.sub.2 containing Y.sub.2 O.sub.3 and CeO.sub.2,
carbide powder, nitride powder and carbonitride powder of IVa, Va, VIa
group metals and SiC powder, having an average particle size of from 0.1
to 2 .mu.m, and SiC whisker, having a length of from 15 to 50 .mu.m and a
diameter of from 0.4 to 2 .mu.m and containing at least 70% whiskers of an
aspect ratio of from 35 to 40 as the controllers. Samples of the Al.sub.2
O.sub.3 based ceramic composite of the present invention were prepared by
first blending the promoters into Al.sub.2 O.sub.3 powder at a ratio shown
in Table 11 (ratio to the overall mixture)1, mixing the same on a ball
mill for 72 hours, then carrying out a heat treatment in the air under
conditions as shown in Table 12, then blending controllers other than SiC
whisker into the treat-treated mixture at a ratio as shown in Table 11,
mixing the same on a wet ball mill for 24 hours into slurry, blending SiC
whisker at a ratio shown in Table 11, wet-mixing for two hours by means of
ultrasonic waves and mechanical mixing, and after drying, hot-pressing the
same under conditions shown in Table 12.
For comparison purposes, furthermore, samples of the conventional Al.sub.2
O.sub.3 based ceramic composite were prepared by using
the above-mentioned Al.sub.2 O.sub.3 powder, ZrO.sub.2 powder, HfO.sub.2
powder, partially stabilized ZrO.sub.2 powder and partially stabilized
HfO.sub.2 powder containing Y.sub.2 O.sub.3 and CeO.sub.2, and SIC whisker
as the raw material powders, mixing these raw material powders under the
same conditions so as to achieve a blended composition as shown in Table
11, and hot-testing the blend under conditions as shown in Table 12
without applying a heat treatment.
TABLE 11
__________________________________________________________________________
Blending composition (% by weight)
Additives promoting .alpha.-Al.sub.2 O.sub.3 platelet formation
Li, K, Na, Ca, Sr, Ba-
compounds Si-compounds
Con- Con-
Components controlling the grain growth of
.alpha.-Al.sub.2 O.sub.3 platelets
vert vert
Unstabilized and IVa, Va, IVa
into into
partially stabilized
SiC compounds
Amount oxide
Amount oxide
ZrO.sub.2 /HfO.sub.2
whisker
and SiC Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics
of present
invention
1 CaCO.sub.3 : 0.05
0.02
Si(OCH3).sub.4 : 0.1
0.07
ZrO.sub.2 : 5 25 TiCN: 10 Remainder
Si(OC.sub.2 H.sub.5).sub.4 : 0.1
2 SrCO.sub.3 : 02
0.14
SiO.sub.2 : 0.2
0.20
ZrO.sub.2 : 15 15 SiC: 10 Remainder
3 CaCl.sub.2 : 02
0.10
SiO.sub.2 : 0.02
0.02
ZrO.sub.2 : 10 15 TiC: 5, TiN:
Remainder
4 BaCl.sub.2 : 2.7
2.00
SiO.sub.2 : 1.5
1.50
HfO.sub.2 : 15 20 SiC: 5 Remainder
5 SrCl.sub.2 : 1.0
0.65
SiO.sub.2 : 0.4
0.40
ZrO.sub.2 : 15 15 ZrN: 10 Remainder
6 CaO: 1.5 1.50
SiO.sub.2 : 1.0
1.00
ZrO.sub.2 : 10, ZrO.sub.2 (Y.sub.2 O.sub.3 :
2 mol %): 5 20 ZrC: 5 Remainder
7 SrO: 0.4 0.40
SiO.sub.2 : 0.2
0.20
ZrO.sub.2 : 10 15 TiC: 5, TiN: 5, SiC:
Remainder
8 CaCO.sub.3 : 0.1, CaO: 0.1
0.14
SiO.sub.2 : 0.2
0.20
ZrO.sub.2 : 5, HfO.sub.2 :
15 HfCN: 10 Remainder
9 BaCl.sub.2 : 0.4, SrO: 0.2
0.49
SiO.sub.2 : 0.2
0.20
ZrO.sub.2 (CeO.sub.2 : 12 mol %):
15 TiCN: 15 Remainder
ZrO.sub.2 (Y.sub.2 O.sub.3 : 2 mol %): 5
10 BaCO.sub.3 : 0.2,
0.25
SiO.sub.2 : 0.2
0.20
ZrO.sub.2 : 15 10 WC: 15 Remainder
CaCl.sub.2 : 0.1,
Sr(NO.sub.3).sub.2 : 0.1
11 Sr(NO.sub.3).sub.2 : 0.2
0.37
SiO.sub.2 : 0.3
0.35
HfO.sub.2 (Y.sub.2 O.sub.3 : 2 mol %):
20 TiCN: 15 Remainder
SrCO.sub.3 : 0.1, BaO: 0.2
Si(OC.sub.3 H.sub.7).sub.4 : 0.2
12 Na.sub.2 CO.sub.3 : 0.1
0.06
SiO.sub.2 : 0.1
0.10
ZrO.sub.2 : 15 15 NbC: 10 Remainder
13 LiNO.sub.3 : 0.5,
0.68
SiO.sub.2 : 0.5
0.50
HfO.sub.2 : 15 20 TaN: 5 Remainder
SrCO.sub.3 : 0.5
14 BaC.sub.2 O.sub.4 H.sub.2 O: 2.0
1.26
SiO.sub.2 : 1.5
1.50
-- 25 TiCN: 15 Remainder
15 Li.sub.2 CO.sub.3 : 0.05,
0.04
SiO.sub.2 : 0.1
0.10
-- 10 TiN: 10 Remainder
Na.sub.2 SO.sub.4 : 0.5
Con-
ventional
ceramics
1 -- -- -- -- ZrO.sub.2 (Y.sub.2 O.sub.3 : 2 mol %):
15 TiCN: 10 Remainder
2 -- -- -- -- HfO.sub.2 : 10 20 TiC: 10, TiCN:
Remainder
3 -- -- -- -- ZrO.sub.2 (CeO.sub.2 : 12 mol %):
10 TiN: 5, SiC:
Remainder
ZrO.sub.2 (Y.sub.2 O.sub.3 : 2 mol %): 10
4 -- -- -- -- ZrO.sub.2 : 10 15 TiC: 10, TiC:
Remainder
SiC: 5
__________________________________________________________________________
TABLE 12
__________________________________________________________________________
Heat treatment
Hot pressing Flank .alpha.-Al.sub.2 O.sub.3
grain Bending
Fracture
Temperature
Time
Temperature
Pressure
Time
wear morphology
strength
toughness
(.degree.C.)
(Hr)
(.degree.C.)
(MPa)
(Hr)
(mm) Shape
Size (.mu.m)
(MPa)
(MPa
__________________________________________________________________________
m.sup.1/2)
Ceramics of present invention
1 600 1 1850 40 2 0.30 Platelet
2 840 6.9
2 800 1 1750 30 2 0.30 Platelet
2 840 6.7
3 1050 1 1850 30 2 0.32 Platelet
2 870 6.8
4 900 2 1750 30 1 0.36 Platelet
1 850 7.0
5 900 1 1800 30 2 0.30 Platelet
1 880 7.1
6 600 2 1650 30 2 0.29 Platelet
2 860 6.8
7 800 1 1750 30 2 0.28 Platelet
1 840 7.0
8 800 1 1750 30 2 0.28 Platelet
1 810 7.0
9 800 1 1800 20 2 0.31 Platelet
1 840 6.6
10 900 1 1800 30 2 0.29 Platelet
1 870 6.9
11 1000 1 1750 30 2 0.31 Platelet
1 9DO 7.1
12 600 1 1750 30 2 0.29 Platelet
2 860 7.1
13 600 2 1750 30 2 0.30 Platelet
1 880 7.0
14 900 2 1750 30 2 0.30 Platelet
2 870 7.2
15 800 1 1750 30 2 0.32 Platelet
2 890 7.0
Conventional
ceramics
1 -- -- 1750 30 2 Fractured in 12 min.
Equiaxed
1 830 5.4
2 -- -- 1750 30 2 Fractured in 15 min.
Equiaxed
1 810 5.9
3 -- -- 1800 30 2 Fractured in 10 min.
Equiaxed
1 850 5.4
4 -- -- 1700 30 2 Fractured in 17 min.
Equiaxed
1 840 5.7
__________________________________________________________________________
Subsequently, a cast iron milling test was carried out under the same
conditions as in the Example 4 for the thus obtained samples of the
various ceramics. The results are shown in Table 12. The shape, particle
size, bending strength and fracture toughness of .alpha.-Al.sub.2 O.sub.3
grains and also shown in Table 12.
As is clear from Table 12, the ceramics of the present invention, having a
structure in which Al.sub.2 O.sub.3 grains have grown into platelets, have
a strength of the same order as that of the conventional ceramics, but are
superior in toughness. This is reflected in the fact that the ceramics of
the present invention are free from occurrence of breakage or chipping in
wet milling of cast iron and display excellent wear resistance for a long
period of time.
(EXAMPLE 7)
Using the same raw materials as in the Examples 1 and 2, a liquid phase was
prepared as shown in Table 13, by first blending the promoters and
Al.sub.2 O.sub.3 powder, and after mixing the same on a ball mill for 72
hours, heat-treating the mixture in the air. After grinding this liquid
phase, the liquid phone, Al.sub.2 O.sub.3 powder and the controllers were
blended, mixed on a ball mill for 72 hours, and after drying, the mixture
was press-formed into pressurized powder of a prescribed shape under a
pressure of 1 ton/cm.sup.2. Samples of Al.sub.2 O.sub.3 --ZrO.sub.2 based
ceramics of the present invention were prepared by sintering the formed
mixture for an hour at a temperature shown in Table 14.
TABLE 13
__________________________________________________________________________
Blending composition (% by weight)
Composition of additives for liquid forming, and its content
Li, K, Na, Ca, Sr, Ba- Heat
compounds Si-compounds
Al.sub.2 O.sub.3
treatment Components controlling
Con- Con- Con-
Tem- the grain
vert vert vert
per- growth of .alpha.-Al.sub.2
O.sub.3 platelets
into into into
ature
Time Unstabilized and partially
Amount oxide
Amount oxide
Amount
oxide
(.degree.C.)
(Hr)
Content
stabilized ZrO.sub.2
/HfO.sub.2 Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics
of present
invention
1 CaCO.sub.3 : 50
35 SiO.sub.2 : 40
51 10 14 1400
2 1 ZrO.sub.2 :
Remainder
2 BaCO.sub.3 : 50
44 SiO.sub.2 : 40
45 10 11 1500
2 2 ZrO.sub.2 (Y.sub.2 O.sub.3 :
2 mol %): 40 Remainder
3 SrCO.sub.3 : 70
61 SiO.sub.2 : 20
26 10 13 1350
2 2 ZrO.sub.2 :
Remainder
4 Ca(NO.sub.3).sub.2 : 70
42 SiO.sub.2 : 20
39 10 19 1400
2 3 ZrO.sub.2 (CeO.sub.2 : 12
mol %): 25 Remainder
5 Ba(NO.sub.3).sub.2 : 35
48 Si(OC.sub.2 H.sub.5).sub.4 : 60
40 5 12 1400
2 2 ZrO.sub.2 :
Remainder
6 CaO: 15, SrO: 15
30 SiO.sub.2 : 55
55 15 15 1400
4 3 ZrO.sub.2 (Y.sub.2 O.sub.3 :
3 mol %): 10,
Remainder
ZrO.sub.2 : 10
7 Na.sub.2 CO.sub.3 : 45
30 SiO.sub.2 : 50
65 5 5 1200
4 1 ZrO.sub.2 :
Remainder
8 K2NO.sub.3 : 40
24 SiO.sub.2 : 55
70 5 6 1150
2 0.5 HfO.sub.2 :
Remainder
9 CaO: 30 30 SiO.sub.2 : 58
58 12 12 1300
3 2 ZrO.sub.2 :
Remainder
10 SrCl.sub.2 : 55
45 SiO.sub.2 : 35
43 10 12 1350
2 4 HfO.sub.2 (Y.sub.2 O.sub.3 :
3 mol %): 10 Remainder
11 BaCl.sub.2 : 20, Li.sub.2 SO.sub.4 : 20
31 SiO.sub.2 : 40
61 5 8 1250
2 1 ZrO.sub.2 (Y.sub.2 O.sub.3 :
2 mol %): 30 Remainder
12 BaCO.sub.3 : 30, SrCO.sub.3 : 20
43 SiO.sub.2 : 40
46 10 11 1400
2 2 ZrO.sub.2 : 10, HfO.sub.2 :
10 Remainder
__________________________________________________________________________
Samples of conventional Al.sub.2 O.sub.3 --ZrO.sub.2 based sintered
ceramics were prepared in the same manner as in the Example 1.
Subsequently, a cutting test was carried out under the same conditions as
in the Example 1 for various samples obtained as above. The shape,
particle size, bending strength and fracture toughness of .alpha.-Al.sub.2
O.sub.3 grains ace also shown in Table 14.
As is clear from Table 14, the ceramics of the present invention, having a
structure in which Al.sub.2 O.sub.3 grains have grown into platelets, have
an improved toughness over that of the conventional ceramics. This is
reflected in the fact that, in spite of the almost equal cutting
properties exhibited in continuous cutting of steel, the conventional
ceramics suffers from breakage in the cutting edge in discontinuous
cutting of steel in all cases, whereas all samples of the present
invention are free from breakage or chipping in the cutting edge and
displays an excellent wear resistance for a long period of time.
(EXAMPLE 8)
A liquid phase was prepared, as shown in Table 15, by using the game raw
materials as in the Example 6, blending the promoters and Al.sub.2 O.sub.3
a powder, and after mixing the blend on a ball mill for 72 hours,
heat-treating and grinding the mixture in the air. Mixed powder was
obtained by blending this liquid phase with the controllers other than SiC
whisker, mixing the blend on a wet ball mill for 24 hours into slurry,
blending SiC whisker into the mixture, wet-mixing the same for 24 hours by
means of ultrasonic waves and mechanical mixing, and drying the same.
Samples of Al.sub.2 O.sub.3 based ceramic composite of the present
invention were prepared by hot-pressing this mixed powder under conditions
as shown in Table 16.
TABLE 14
__________________________________________________________________________
Sintering
Flank wear .alpha.-Al.sub.2 O.sub.3 grain
Bending
Fracture
temperature
(mm) morphology
strength
toughness
(.degree.C.)
Interrupt
Continuous
Shape
Size (.mu.m)
(MPa)
(MPa m.sup.1/2)
__________________________________________________________________________
Ceramics of present invention
1 1650 0.30 0.27 Platelet
9 730 5.2
2 1700 0.31 0.24 Platelet
3 900 5.1
3 1600 0.26 0.21 Platelet
4 860 5.4
4 1550 0.28 0.23 Platelet
3 780 5.0
5 1700 0.31 0.19 Platelet
12 790 5.5
6 1550 0.28 0.18 Platelet
3 760 5.4
7 1400 0.26 0.21 Platelet
3 750 5.6
8 1500 0.25 0.20 Platelet
6 800 5.2
9 1600 0.27 0.22 Platelet
4 810 5.2
10 1450 0.28 0.26 Platelet
7 760 5.0
11 1500 0.30 0.24 Platelet
3 890 5.2
12 1600 0.31 0.23 Platelet
4 7SO 5.5
__________________________________________________________________________
TABLE 15
__________________________________________________________________________
Blending composition (% by weight)
Composition of additives for liquid forming, and its content
Li, K, Na, Ca, Sr, Ba- Heat Components controlling the
grain
compounds Si-compounds
Al.sub.2 O.sub.3
treatment growth of .alpha.-Al.sub.2
O.sub.3 platelets
Con- Con- Con-
Tem- Unstabilized
vert vert vert
per- and partially
IVa, Va, VIa
into into into
ature
Time stabilized
SiC compounds
Amount oxide
Amount oxide
Amount
oxide
(.degree.C.)
(Hr)
Content
ZrO.sub.2 /HfO.sub.2
whisker
and
Al.sub.2
__________________________________________________________________________
O.sub.3
Ceramics
of present
invention
1 CaCO.sub.3 : 50
35 SiO.sub.2 : 40
51 10 14 1400
2 1 ZrO.sub.2 : 10
20 -- Remainder
2 BaCO.sub.3 : 50
44 SiO.sub.2 : 40
45 10 11 1500
2 2 ZrO.sub.2 (Y.sub.2 O.sub.3 :
20 -- Remainder
2 mol %): 20
3 SrCO.sub.3 : 70
61 SiO.sub.2 : 20
26 10 13 1350
2 2 ZrO.sub.2 : 20
20 -- Remainder
4 Ca(NO.sub.3).sub.2 : 70
42 SiO.sub.2 : 20
39 10 19 1400
2 3 ZrO.sub.2 (CeO.sub.2 :
15 -- Remainder
12 mol %):
25
5 Ba(NO.sub.3).sub.2 : 35
48 Si(OC.sub.2 H.sub.5).sub.4 : 60
40 5 12 1400
2 2 -- 20 TiC:
Remainder
6 CaO: 15
30 SiO.sub.2 : 55
55 15 15 1400
4 3 ZrO.sub.2 : 10
15 TiN:
Remainder
SrO: 15
7 Na.sub.2 CO.sub.3 : 45
32 SiO.sub.2 : 55
68 0 0 1200
4 1 -- 25 -- Remainder
8 K2NO.sub.3 : 40
24 SiO.sub.2 : 55
70 5 6 1150
2 0.5 -- 20 TiN:
Remainder
9 CaO: 30
30 SiO.sub.2 : 58
58 12 12 1300
3 2 ZrO.sub.2 : 20
15 SiC:
Remainder
10 SrCl.sub.2 : 55
45 SiO.sub.2 : 35
43 10 12 1350
2 4 ZrO.sub.2 : 10
20 TiC:
Remainder
11 BaCl.sub.2 : 20
31 SiO.sub.2 : 40
61 5 8 1250
2 1 ZrO.sub.2 (Y.sub.2 O.sub.3 :
15 WC:
Remainder
Li.sub.2 SO.sub.4 : 20 2 mol %): 15
12 BaCO.sub.3 : 30
45 SiO.sub.2 : 40
46 10 11 1400
2 2 ZrO.sub.2 : 20
10 TiN:
Remainder
SrCO.sub.3 : 20
__________________________________________________________________________
Samples of the conventional Al.sub.2 O.sub.3 based ceramic composite were
prepared in the same manner as in the Examples 4, 5 and 6.
Subsequently, for samples prepared as mentioned above, a milling test of
case iron was carried out under the same conditions as in the Examples 4,
5 and 6. The results are shown in Table 16. The shape, particle size,
bending strength and fracture toughness of .alpha.-Al.sub.2 O.sub.3 grains
are also shown in Table 16.
As is clear from Table 16, the ceramics of the present invention, having a
structure in which Al.sub.2 O.sub.3 grains have grown into platelets, have
a strength of the same order as that of the conventional ceramics, but are
superior in toughness, and this is reflected in the fact that the ceramics
of the present invention are free from occurrence of breakage or chipping
in wet milling of cast iron and display excellent wear resistance for a
long period of time.
(EXAMPLE 9)
A surface-coated ceramics made by forming a hard coating layer on the
surface of Al.sub.2 O.sub.3 based ceramic composite comprising platelet
.alpha.-Al.sub.2 O.sub.3 will now be described by means of an example
covering the case of a cutting tool.
A cutting tool made of surface-coated Al.sub.2 O.sub.3 based ceramic
composite of the present invention (hereinafter referred to as the "coated
cutting tool of the invention") was prepared by forming a hard coating
layer having a chemical composition and an average thickness as shown in
Table 17, which comprised a single layer or multiple layers of Ti carbide,
nitride, carbonitride, carbonate and carbonate-nitrides and Al oxide under
a reduced pressure of up to 100 torr at a temperature of from 950.degree.
C. to 1,050.degree. C. on the surface of the substrate made of the
ceramics of the present invention having the shape of the previously
mentioned cutting tool JIS SNGN 120408, by using an ordinary chemical
vapor depositing apparatus.
TABLE 16
__________________________________________________________________________
Hot Pressing Flank
.alpha.-Al.sub.2 O.sub.3 grain
Bending
Fracture
Temperature
Pressure
Time
wear
morphology
strength
toughness
(.degree.C.)
(MPa)
(Hr)
(mm)
Shape
Size (.mu.m)
(MPa)
(MPa m.sup.1/2)
__________________________________________________________________________
Ceramics of present invention
1 1750 30 2 0.33
Platelet
2 800 7.0
2 1750 30 2 0.34
Platelet
1 840 7.3
3 1750 30 1 0.32
Platelet
1 820 7.1
4 1600 30 2 0.33
Platelet
1 800 7.2
5 1850 30 1 0.35
Platelet
1 850 7.4
6 1800 25 2 0.34
Platelet
1 900 7.0
7 1800 30 2 0.31
Platelet
3 820 7.2
8 1750 30 1 0.32
Platelet
2 850 7.4
9 1750 30 2 0.31
Platelet
1 850 6.5
10 1750 30 2 0.33
Platelet
1 870 7.4
11 1800 40 1 0.35
Platelet
1 920 7.3
12 1750 30 1 0.37
Platelet
1 800 7.2
__________________________________________________________________________
TABLE 17
__________________________________________________________________________
Blending composition of ceramic substrates (% by weight)
Additives promoting
Examples .alpha.-Al.sub.2 O.sub.3 platelet
Components controlling
Example
Sample
Li, Na, K, Ca, Sr, Ba-
the grain growth of
No. No. compounds SiO.sub.2
.alpha.-Al.sub.2 O.sub.3
Al.sub.2 O.sub.3
__________________________________________________________________________
Coated ceramic cutting tools of
present invention
1 1 1 SrCO.sub.3 : 0.4
0.3
ZrO.sub.2 : 20
Remainder
2 1 13 LiNO.sub.3 : 0.09
0.2
HfO.sub.2 (Y.sub.2 O.sub.3 : 3 mol
%): 20 Remainder
3 3 8 K.sub.2 SO.sub.4 : 0.4, SrCO.sub.3 :
0.4
ZrO.sub.2 (CeO.sub.2 : 12 mol %):
Remainder
TiN: 20
4 3 9 SrCO.sub.3 : 0.5
0.5
SiC: 20 Remainder
5 3 14 K2SO.sub.4 : 0.1, Na.sub.2 SO.sub.4 :
0.3
TiCN: 20 Remainder
6 4 4 Ca(NO.sub.3).sub.2 : 0.15
0.02
SiC whisker: 20
Remainder
7 5 13 BaC.sub.2 O.sub.4 H.sub.2 O: 1.0
1.0
ZrO.sub.2 : 15
Remainder
SiC whisker: 25
Conventional coated
ceramic cutting tools
1 1 2 -- -- ZrO.sub.2 : 20
Remainder
2 3 3 -- -- HfO.sub.2 : 10
Remainder
SiC: 10
3 3 5 -- -- TiCN: 30 Remainder
4 4 3 -- -- SiC whisker 30
Remainder
Comparative uncoated
ceramic cutting tools
1 1 15 BaC.sub.2 O.sub.4 H.sub.2 O: 0.4
0.2
ZrO.sub.2 : 20
Remainder
2 3 1 BaCO.sub.3 : 0.5
0.3
ZrO.sub.2 (Y.sub.2 O.sub.3 : 3 mol
%): 15 Remainder
TiCN: 10
3 3 14 K.sub.2 SO.sub.4 : 0.1, Na.sub.2 SO.sub.4 :
0.3
TiCN: 25 Remainder
4 4 4 Ca(NO.sub.3).sub.2 : 0.15
0.05
SiC whisker: 20
Remainder
ZrO.sub.2 : 5
5 5 1 CaCO.sub.3 : 0.05
0.02
SiC whisker: 30
Remainder
__________________________________________________________________________
Hard coating layer
1st 2nd 3rd 4th 5th
layer
layer
layer layer
layer Flank wear
(.mu.m)
(.mu.m)
(.mu.m)
(.mu.m)
(.mu.m)
(mm)
__________________________________________________________________________
Coated ceramic cutting tools of
present invention
1 TiN: 2
Al.sub.2 O.sub.3 : 3
-- -- -- 0.34
2 Al.sub.2 O.sub.3 : 2
TiC: 1
-- -- -- 0.35
3 TiC: 6
TiCNO: 2
Al.sub.2 O.sub.3 : 2
-- -- 0.36
4 TiC: 6
TiCN: 2
TiCNO: 1
-- -- 0.37
5 TiCN: 2
Al.sub.2 O.sub.3 : 3
TiN: 1 -- -- 0.33
6 TiC: 4
TiCNO: 2
Al.sub.2 O.sub.3 : 2
-- -- 0.37
7 TiCN: 2
TiC: 3
Al.sub.2 O.sub.3 : 2
TiCNO: 1
TiCNO: 2
0.37
Conventional coated
ceramic cutting tools
1 TiN: 2
Al.sub.2 O.sub.3 : 3
-- -- -- Fractured in 5 min.
2 TiN: 2
Al.sub.2 O.sub.3 : 3
Al.sub.2 O.sub.3 : 2
TiCNO: 1
TiCN2 Fractured in 4 min.
3 TiCN: 2
Al.sub.2 O.sub.3 : 3
TiN: 1 -- -- Fractured in 2 min.
4 Al.sub.2 O.sub.3 : 2
TiC: 1
-- -- -- Fractured in 10 min.
Comparative uncoated
ceramic cutting tools
1 -- -- -- -- -- The useful life time of
this tool was 10 min. of
cutting because the wear
was above 0.4 mm.
2 -- -- -- -- -- The useful life time was
6 min.
3 -- -- -- -- -- The useful life time was
8 min.
4 -- -- -- -- -- The useful life time was
6 min.
5 -- -- -- -- -- The useful life time was
5 min.
__________________________________________________________________________
A cutting tool made of conventional surface coated Al.sub.2 O.sub.3 based
ceramics (hereinafter referred to as the "conventional coated cutting
tool" was prepared by forming a hard coating layer by the above-mentioned
chemical vapor deposition on the surface of the above-mentioned
conventional Al.sub.2 O.sub.3 based ceramic substrate of cutting tool
having a chemical composition outside the scope of the Al.sub.2 O.sub.3
based ceramic composite of the present invention.
For these coated tools, a high-speed continuous cutting test of steel was
carried out under conditions:
Material to be cut: SCM440 (hardness: HB250),
Cutting speed: 420 mm/min,
Feed: 0.36 mm/rev,
Depth of cut: 2 mm, and
Wet cutting time: 15 minutes,
and wear of the relief face of the cutting edge was measured. The results
are shown in Table 17. For comparison purposes, a similar cutting test was
carried out on a cutting tool made of the Al.sub.2 O.sub.3 based ceramic
composite of the present invention having no hard coating layer formed
thereon (hereinafter referred to as the "comparative cutting tool"). The
results are also shown in Table 17.
As is evident from the results shown in Table 17 while the coated cutting
tool of the invention exhibits an excellent wear resistance under the
effect of the hard coating layer excellent in adherence even in wet
high-speed cutting of steel, which requires a high wear resistance, the
conventional coated cutting tool shows only a very limited service life
because of the breakage resulting from the poor toughness of the
substrate. In the comparative cutting tool having no hard coating layer,
the service life is limited by the wear of the relief face in a very short
period of time as a result of a poor wear resistance. In this Example, the
moment when the worn width became 0.4 mm was considered the end of the
service life.
Having described preferred embodiments of the invention with reference to
the accompanying drawings, it is to be understood that the invention is
not limited to those precise embodiments, and that various changes and
modifications may be effected therein by one skilled in the art without
departing from the scope or spirit of the invention as defined in the
appended claims.
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